I was going to go with the first (and cheaper) first one, but looking into it loads of people are raving about the second one... And personally, I can't see why.
The difference is that the cheaper board uses nForce 680i LT chipset, which is a scaled back version of the 680i chipset on the other board.
You should read the detailed comparison and review here. I skipped through it quickly and it seems that the features missing on the cheaper board are those most people wouldn't need, and it should be just fine.
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